Gel Point Determination in Curing Polydimethylsiloxane Polymer Networks by Longitudinal Ultrasonic Waves

1988 ◽  
Vol 142 ◽  
Author(s):  
A. Shefer ◽  
G. Gorodetsky ◽  
M. Gottlieb
Keyword(s):  
Polymer Networks ◽  
Ultrasonic Waves ◽  
Acoustic Properties ◽  
Gel Point ◽  
Longitudinal Waves ◽  
Infra Red ◽  
Acoustic Interferometer ◽  
Point Determination ◽  
Longitudinal Ultrasonic Waves

AbstractThe formation of well characterized poly-dimethylsiloxane networks has been studied by means of an acoustic interferometer. The hydrosilation reaction used to form these networks was followed by infra red spectroscopy. The relative changes in velocity of the ultrasonic longitudinal waves propagating through the system are found to be very sensitive to gelation and to the density of crosslinks. Due to our simultaneous kinetic and ultrasonic studies it was possible to relate the changes in acoustic properties of the curing system directly to the cure state.

Ultrasonic dispersion in halo-ethylene vapours

1955 ◽  
Vol 232 (1191) ◽  
pp. 537-547 ◽  
Keyword(s):  
Virial Coefficient ◽  
Vinylidene Fluoride ◽  
Vibrational Energy ◽  
Relaxation Times ◽  
Second Virial Coefficient ◽  
Ultrasonic Waves ◽  
Ultrasonic Dispersion ◽  
Infra Red ◽  
Acoustic Interferometer ◽  
Inactive Mode

The velocity and absorption of ultrasonic waves have been measured by acoustic interferometer in the vapours of vinyl fluoride, chloride, bromide and iodide, vinylidene fluoride, cis -dichloro-ethylene, trans -dichloro-ethylene, trichloro-ethylene and tetrafluoro-ethylene at 100° C and for values of f|p ranging from 100 kc s -1 atm -1 to 15 Mc s ~1 atm~1. All show dispersion or incipient dispersion, and single relaxation times appear to control the whole of the molecular vibrational energy in each case. The results are correlated with previous results for halo-methane vapours and for other polyatomic molecules. The conclusion is drawn that vibrational activation enters a molecule via the mode of lowest frequency. The probability of excitation of that mode in collision is a function both of its frequency and of the intensity of its infra-red activity. In most cases a strongly infra-red active mode is very much more easily excited by collision than an inactive mode of the same frequency. The paper includes second virial coefficient data for all the vapours investigated.

Study of Curing Processes in PDMS at Various Stoichiometric Ratios by Longitudinal Ultrasonic Waves

1989 ◽  
Vol 177 ◽  
Author(s):  
A. Shefer ◽  
G. Gorodetsky ◽  
M. Gottlieb
Keyword(s):  
Wave Propagation ◽  
Bulk Modulus ◽  
Longitudinal Wave ◽  
Wave Velocity ◽  
Ultrasonic Waves ◽  
Gel Point ◽  
Longitudinal Wave Velocity ◽  
Stoichiometric Ratios ◽  
Longitudinal Ultrasonic Waves

ABSTRACTCuring reactions of linear vinyl terminated poly(dimethylsiloxane) with a four functional hydride silane crosslinker at various stoichiometric ratios, were studied by wave propagation at ultrasonic frequencies. Longitudinal wave velocity was found to be sensitive to the covalent endlinking, and gel point in these systems.The observed changes in longitudinal wave velocity during the reaction are governed by changes in the bulk modulus of the system.

Determination of the foaming parameters of polyurethane compositions from the velocity of longitudinal ultrasonic waves

1979 ◽  
Vol 15 (3) ◽  
pp. 316-317 ◽  
Author(s):  
V. M. Mel'nikov ◽  
�. A. Putnin'sh ◽  
V. O. Putninya ◽  
V. P. Karlivan
Keyword(s):  
Ultrasonic Waves ◽  
Longitudinal Ultrasonic Waves

The relation between the velocity of longitudinal ultrasonic waves and the strengths of rocks and ores in the sheregesh deposit (Gornaya Shoriya)

1966 ◽  
Vol 2 (4) ◽  
pp. 425-427
Author(s):  
V. V. Andrievich ◽  
S. E. Mogilevskaya ◽  
S. T. Nakhrov ◽  
G. P. Starkov
Keyword(s):  
Ultrasonic Waves ◽  
Longitudinal Ultrasonic Waves

The Effect of Hydrostatic Pressure on Physical Properties and Microstructure of Spruce and Cherry

Holzforschung ◽  
2000 ◽  
Vol 54 (1) ◽  
pp. 83-92 ◽  
Author(s):  
Voichita Bucur ◽  
Simone Garros ◽  
Claire Y. Barlow
Keyword(s):  
Hydrostatic Pressure ◽  
Structural Damage ◽  
Untreated Wood ◽  
Average Density ◽  
Ultrasonic Waves ◽  
Ultrasonic Velocities ◽  
Main Effect ◽  
Natural Wood ◽  
Effect Of Hydrostatic Pressure ◽  
Longitudinal Ultrasonic Waves

Summary The effect of hydrostatic pressure on the density, the ultrasonic velocities and the microstructure of spruce and cherry wood has been studied. Generally speaking, under hydrostatic pressure wood becomes less heterogeneous and less anisotropic than natural wood. In spruce, crushing and buckling of the thin-walled cells in the earlywood takes place. This also has the effect of disrupting the medullary rays, which assume a zig-zag path through the structure. Cherry has a much more homogeneous structure, and the main effect of the hydrostatic pressure is compaction of the vessels by buckling of the walls. The fibres are scarcely affected by the treatment. The width of the earlywood zone decreased after the application of pressure by 26% in spruce, and by 11% in cherry. The average density was increased by the hydrostatic pressure by 26% for spruce and by 46% for cherry. The densitometric profile of spruce demonstrates significant changes following the pressure treatment, with the minimum density DMin increasing and the maximum density DMax decreasing. For cherry, the densitometric profile is shifted rather uniformly towards higher densities, and the annual ring profile is spatially slightly compacted but otherwise similar to that of untreated wood. The anisotropy of wood (expressed by the ratio of acoustic invariants) decreased by 56% for spruce and by 33% for cherry. The structural damage in spruce is predominantly found in the radial (R) direction, and this corresponds to a reduction of 73% in the velocity of the longitudinal ultrasonic waves in the radial direction, VRR. In cherry, the structural damage is mainly in the transverse, T direction. The velocity of the longitudinal ultrasonic waves in the transverse direction, VTT is reduced by 44%. The medullary rays in cherry seem to be the most important anatomical feature influencing the propagation of ultrasonic waves.

Gel point determination of a thermoset prepreg by means of rheology

2019 ◽  
Vol 78 ◽  
pp. 105950 ◽  
Author(s):  
M.R. Martínez-Miranda ◽  
V. García-Martínez ◽  
M.R. Gude
Keyword(s):  
Gel Point ◽  
Point Determination
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